using System;

using System.Linq;

public class Program

{

    public static void Main()

    {

            long num =600851475143;

            //FermatFactors(num);

        for(int counter=2;counter<=Math.Sqrt(num);counter++)

        {

            if(num%counter==0)

            {

                num=num/counter;

                counter--;

            }

        }

        if(num>=2)

        {

            Console.WriteLine(num);

        }

    }

     static void FermatFactors(long n)  

    {  

        // since fermat's factorization applicable  

        // for odd positive integers only  

        if(n <= 0)  

        {  

            Console.Write("["+ n + "]");  

            return;  

        }  

        // check if n is a even number  

        if((n & 1) == 0)  

        {  

            Console.Write("[" + n / 2.0 + "," + 2 + "]");  

            return;  

        }  

        var a = (int)Math.Ceiling(Math.Sqrt(n)) ;  

        // if n is a perfect root,  

        // then both its square roots are its factors  

        if(a * a == n)  

        {  

            Console.Write("[" + a + "," + a + "]");  

            return;  

        }  

        int b;  

        while(true)  

        {  

            var b1 = a * a - n ;  

            b = (int)(Math.Floor(Math.Sqrt(b1))) ;  

            if(b * b == b1)  

                break;  

            else

                a += 1;  

        }  

        Console.Write("[" + (a - b) +"," + (a + b) + "]" );  

        return;  

    } 

}